This study will examine the regulation of luteinizing hormone (LH), follicle stimulating hormone (FSH) and sperm formation in men. LH and FSH are hormones that are made and released by the pituitary gland. LH regulates the synthesis and release of testosterone by the testes and FSH stimulates the testes to form sperm. Under normal circumstances both LH and FSH are released in pulses throughout the day and night. We will study LH and FSH release and correlate our findings with testosterone secretion and sperm production by the testes. The purpose of this study is to examine the relationship between LH and FSH secretion, testosterone levels, and sperm production in both reproductively normal men and in men with reproductive dysfunction.